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2-Mercaptoimidazole covalently bonded to a silica gel surface for the selective separation of mercury(II) from an aqueous solution

Dias, N. L.; Gushikem, Y.
Fonte: Marcel Dekker Inc Publicador: Marcel Dekker Inc
Tipo: Artigo de Revista Científica Formato: 2535-2545
ENG
Relevância na Pesquisa
36.04%
Silica gel with a specific surface area of 365 m(2).g(-1) and an average pore diameter of 60 Angstrom was chemically modified with 2-mercaptoimidazole. The degree of functionalization of the covalently attached molecule, (drop SiO)(3)(CH2)(3) - MI, where MI is the 2-mercaptoimidazole bound to the silica surface by a propyl group, was 0.58 mmolg.(-1). In individual metal adsorption experiments from aqueous solutions by the batch procedure, the affinity order was Hg(II)much greater than Cd-II > Cu-II approximate to Zn-II approximate to Pb-II > Mn-II at solution pHs between 4 and 7. Due to the high affinity by the sulfur atom, Hg-II is strongly bound to the functional groups. When solution containing a mixture of Hg-II, Cd-II, Cu-II, Zn-II, Pb-II, and Mn-II ions was passed through a column packed with the adsorbent, Hg-II was the only one whose adsorption and elution was not affected by the presence of other ions.

Selective functionalization of electrospun fibres

Girão, André Francisco Oliveira
Fonte: Universidade de Lisboa Publicador: Universidade de Lisboa
Tipo: Dissertação de Mestrado
Publicado em //2013 ENG
Relevância na Pesquisa
36.26%
Tese de mestrado integrado em Engenharia Biomédica e Biofísica, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2013; A engenharia de tecidos é uma área multidisciplinar da engenharia biomédica que articula conceitos da química, física, engenharia e medicina com o objetivo de recuperar ou substituir uma função perdida de determinado órgão ou tecido. Um dos principais desafios desta área da biotecnologia é a criação de matrizes tridimensionais biocompatíveis e biodegradáveis que sejam capazes de garantir um suporte físico e bioquímico adequado à regeneração celular. Assim, as características mecânicas, químicas e biológicas destas matrizes devem ser adaptadas ao ambiente celular que se pretende reproduzir, dando origem quer à resposta celular específica das células cultivadas na matriz, quer à otimização da resposta fisiológica do próprio organismo. Com efeito, dependendo da função a que se destina, as matrizes usadas em engenharia de tecidos variam tanto no biomaterial que lhes dá origem como na técnica de fabricação utilizada. As vantagens dos polímeros face aos outros materiais tais como biocompatibilidade, biodegradação, alta porosidade e boas propriedades mecânicas...

Mechanism of the selective functionalization of saturated hydrocarbons by Gif systems: relationship with methane monooxygenase.

Barton, D H; Csuhai, E; Doller, D; Ozbalik, N; Balavoine, G
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /05/1990 EN
Relevância na Pesquisa
36.11%
Two intermediates, A and B, have been identified in the selective oxidation of saturated hydrocarbons to ketones by Gif-type systems. Intermediate A has been characterized as an Fev species with a secondary iron sigma-bond to carbon; it is captured by four different reagents or transformed into the second intermediate, B, which hydrolyzes to form a secondary alcohol. A mu-oxo Fe2III dimer is proposed as a basis for Gif-type reactivity. If the first iron is involved in the synthesis of intermediate A, the second is used to oxidize intermediate B intramolecularly to a ketal, which on hydrolysis yields a ketone. The enzyme methane monooxygenase shows a remarkable similarity to Gif-type systems in its selective hydrocarbon oxidation, particularly in the case of adamantane.

Selective Functionalization of Independently Addressed Microelectrodes by Electrochemical Activation and Deactivation of a Coupling Catalyst

Devaraj, Neal K.; Dinolfo, Peter H.; Chidsey, Christopher E. D.; Collman, James P.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/02/2006 EN
Relevância na Pesquisa
46.26%
We demonstrate selective functionalization of independently addressed microelectrodes by electrochemical activation and deactivation of a coupling catalyst. 1,2,3-Triazole formation between terminal acetylenes and organic azides is efficiently catalyzed by copper(I) complexes (a Sharpless “click” reaction) while the oxidized copper (II) complexes are inactive. By electrochemically activating or deactivating the catalyst by switching its redox state, we demonstrate control over triazole formation between surface-immobilized azides and ethynylferrocene. The reaction proceeds on the timescale of minutes using sub-micromolar concentration of reactants and catalyst, requires mild potentials for catalyst activation and deactivation, and works in aqueous and mixed aqueous-organic solvents. By appropriate biasing of each electrode, we selectively modify one of two chemically identical 10-μm-wide electrodes separated by 10 μm in an interdigitated array. The ability to switch on or off the reaction by electrical addressing together with the chemoselectivity of this reaction makes Cu(I)-catalyzed triazole formation an ideal method for the chemical modification of multielectrode arrays.

Catalytic site-selective synthesis and evaluation of a series of erythromycin analogs

Lewis, Chad A.; Merkel, Janie; Miller, Scott J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
36.04%
The generation of a series of analogs of Erythromycin A (EryA, 2) is described. In this study, we compared two peptide-based catalysts – one originally identified from a catalyst screen (5), and its enantiomer (ent-5) – for the selective functionalization of EryA. The semi-synthetic analogs were subjected to MIC evaluation with two bacterial strains and compared to unfunctionalized EryA.

Fabrication and Selective Functionalization of Amine-Reactive Polymer Multilayers on Topographically Patterned Microwell Cell Culture Arrays

Broderick, Adam H.; Azarin, Samira M.; Buck, Maren E.; Palecek, Sean P.; Lynn, David M.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.49%
We report an approach to the fabrication and selective functionalization of amine-reactive polymer multilayers on the surfaces of three-dimensional (3-D) polyurethane-based microwell cell culture arrays. ‘Reactive’ layer-by-layer assembly of multilayers using branched polyethyleneimine (BPEI) and the azlactone-functionalized polymer poly(2-vinyl-4,4’-dimethylazlactone) (PVDMA) yielded film-coated microwell arrays that could be chemically functionalized post-fabrication by treatment with different amine-functionalized macromolecules or small molecule primary amines. Treatment of film-coated arrays with the small molecule amine D-glucamine resulted in microwell surfaces that resisted the adhesion and proliferation of mammalian fibroblast cells in vitro. These and other experiments demonstrated that it was possible to functionalize different structural features of these arrays in a spatially resolved manner to create dual-functionalized substrates (e.g., to create arrays having either (i) azlactone-functionalized wells, with regions between the wells functionalized with glucamine, or (ii) substrates with spatially resolved regions of two different cationic polymers). In particular, spatial control over glucamine functionalization yielded 3-D substrates that could be used to confine cell attachment and growth to microwells for periods of up to 28 days and support the 3-D culture of arrays of cuboidal cell clusters. These approaches to dual functionalization could prove useful for the long-term culture and maintenance of cell types for which the presentation of specific and chemically well-defined 3-D culture environments is required for control over cell growth...

Copper-Free Sonogashira Cross-Coupling for Functionalization of Alkyne-Encoded Proteins in Aqueous Medium and in Bacterial Cells

Li, Nan; Lim, Reyna K. V.; Edwardraja, Selvakumar; Lin, Qing
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
36.32%
Bioorthogonal reactions suitable for functionalization of genetically or metabolically encoded alkynes, e.g., copper-catalyzed azide-alkyne cycloaddition reaction (“click chemistry”), have provided chemical tools to study biomolecular dynamics and function in living systems. Despite its prominence in organic synthesis, copper-free Sonogashira cross-coupling reaction suitable for biological applications has not been reported. In this work, we report the discovery of a robust aminopyrimidine-palladium(II) complex for copper-free Sonogashira cross-coupling that enables selective functionalization of a homopropargylglycine (HPG)-encoded ubiquitin protein in aqueous medium. A wide range of aromatic groups including fluorophores and fluorinated aromatic compounds can be readily introduced into the HPG-containing ubiquitin under mild conditions with good to excellent yields. The suitability of this reaction for functionalization of HPG-encoded ubiquitin in E. coli was also demonstrated. The high efficiency of this new catalytic system should greatly enhance the utility of Sonogashira cross-coupling in bioorthogonal chemistry.

Controlling Site Selectivity in Palladium-Catalyzed C–H Bond Functionalization

Neufeldt, Sharon R.; Sanford, Melanie S.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
26.45%
Effective methodology to functionalize C–H bonds requires overcoming the key challenge of differentiating among the multitude of C–H bonds that are present in complex organic molecules. This Account focuses on our work over the past decade toward the development of site-selective Pd-catalyzed C–H functionalization reactions using the following approaches: substrate-based control over selectivity through the use of directing groups (approach 1), substrate control through the use of electronically activated substrates (approach 2), or catalyst-based control (approach 3). In our extensive exploration of the first approach, a number of selectivity trends have emerged for both sp2 and sp3 C–H functionalization reactions that hold true for a variety of transformations involving diverse directing groups. Functionalizations tend to occur at the less-hindered sp2 C–H bond ortho to a directing group, at primary sp3 C–H bonds that are β to a directing group, and, when multiple directing groups are present, at C–H sites proximal to the most basic directing group. Using approach 2, which exploits electronic biases within a substrate, our group has achieved C-2-selective arylation of indoles and pyrroles using diaryliodonium oxidants. The selectivity of these transformations is altered when the C-2 site of the heterocycle is blocked...

Probing the Role of the Vancomycin E-Ring Aryl Chloride: Selective Divergent Synthesis and Evaluation of Alternatively Substituted E-Ring Analogues

Pinchman, Joseph R.; Boger, Dale L.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
36.26%
The selective functionalization of vancomycin aglycon derivatives through conversion of the E-ring aryl chloride to a reactive boronic acid, and its use in the synthesis of a systematic series of vancomycin E-ring analogues are described. The series was used to examine the E-ring chloride impact in binding d-Ala-d-Ala and on antimicrobial activity. In contrast to the reduced activity of the unsubstituted E-ring derivatives, hydrophobic and relatively non-polar substituents approach or match the chloro substituted vancomycin and was insensitive to the electronic character of the substituent (e.g. Cl vs CN/OMe), whereas highly polar substituents fail to provide the enhancements. Moreover, the active permethylated vancomycin aglycon derivatives exhibit VanB VRE antimicrobial activity at levels that approach (typically within 2-fold) their activity against sensitive bacteria. The robust borylation reaction also enabled the functionalization of a minimally protected vancomycin aglycon (N-Boc-vancomycin aglycon), and provides a direct method for the preparation of previously inaccessible analogues.

Enhancing the Detection Limit of Nanoscale Biosensors via Topographically Selective Functionalization

Lifson, Mark A.; Roy, Dhrubajyoti Basu; Miller, Benjamin L.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
36.04%
Nanoscale biosensors have remarkable theoretical sensitivities, but often suffer from sub-optimal limits of detection in practice. This is in part because the sensing area of nanoscale sensors is orders of magnitude smaller than the total device substrate. Current strategies to immobilize probes (capture molecules) functionalize both sensing and non-sensing regions, leading to target depletion and diminished limits of detection. The difference in topography between these regions on nanoscale biosensors offers a way to selectively address only the sensing area. We developed a bottom-up, topographically selective approach employing self-assembled poly(N-isopropylacrylamide) (PNIPAM) hydrogel nanoparticles as a mask to preferentially bind target to only the active sensing region of a photonic crystal (PhC) biosensor. This led to over one order of magnitude improvement in the limit of detection for the device, in agreement with finite element simulations. Since the sensing elements in many nanoscale sensors are topographically distinct, this approach should be widely applicable.

Liposome Surface Functionalization Based on Different Anchoring Lipids via Staudinger Ligation

Vabbilisetty, Pratima; Sun, Xue-Long
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 28/02/2014 EN
Relevância na Pesquisa
36.25%
Liposome surface functionalization facilitates enormous potential applications of liposomes, such as enhanced stability, bioactive liposome conjugates, and targeted drug, gene and image agent delivery. Anchoring lipids are needed for grafting ligands of interest and play important roles in ligands grafting density, liposome stability, and liposome chemical and physical characteristics as well. In this report, glyco-functionalized liposome systems based on two kinds of anchoring lipid, phosphatidylethonalamine (PE) and cholesterol (Chol) were prepared by post chemically selective functionalization via Staudinger ligation. The size and stability of the liposomes were confirmed by dynamic light scattering (DLS). Particularly, the impact of anchor lipids on the stability of glyco-functionalized liposomes was investigated by comparing two different anchor lipids, namely Chol-PEG2000-TP and DSPE-PEG2000-TP. In addition, the encapsulation and releasing capacity of the glycosylated liposome based on the two anchoring lipids were investigated by entrapping 5, 6-carboxyfluorescein (CF) dye and monitoring the fluorescence leakage, respectively. Furthermore, the density and accessibility of grafted carbohydrate residues on the liposome surface were evaluated for the two anchoring lipids-derived liposomes with lectin binding...

Catalyst recognition of cis-1,2-diols enables site-selective functionalization of complex molecules

Sun, Xixi; Lee, Hyelee; Lee, Sunggi; Tan, Kian L.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.44%
Carbohydrates and natural products serve essential roles in nature, and also provide core scaffolds for pharmaceutical agents and vaccines. However, the inherent complexity of these molecules imposes significant synthetic hurdles for their selective functionalization and derivatization. Nature has in part addressed these issues by employing enzymes that are able to orient and activate substrates within a chiral pocket, which dramatically increases both the rate and selectivity of organic transformations. In this article we show that similar proximity effects can be utilized in the context of synthetic catalysts to achieve general and predictable site-selective functionalization of complex molecules. Unlike enzymes, our catalysts apply a single reversible covalent bond to recognize and bind to specific functional group displays within substrates. By combining this unique binding selectivity and asymmetric catalysis, we are able to modify the less reactive axial positions within monosaccharides and natural products.

Diverse Functionalization of Aurora-A Kinase at Specified Surface and Buried Sites by Native Chemical Modification

Rowan, Fiona; Richards, Meirion; Widya, Marcella; Bayliss, Richard; Blagg, Julian
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 05/08/2014 EN
Relevância na Pesquisa
36.13%
The ability to obtain a homogeneous sample of protein is invaluable when studying the effect of alterations such as post-translational modifications (PTMs). Selective functionalization of a protein to investigate the effect of PTMs on its structure or activity can be achieved by chemical modification of cysteine residues. We demonstrate here that one such technique, which involves conversion of cysteine to dehydroalanine followed by thiol nucleophile addition, is suitable for the site-specific installation of a wide range of chemical mimics of PTMs, including acetylated and dimethylated lysine, and other unnatural amino acids. These reactions, optimized for the clinically relevant kinase Aurora-A, readily proceed to completion as revealed by intact protein mass spectrometry. Moreover, these reactions proceed under non-denaturing conditions, which is desirable when working with large protein substrates. We have determined reactivity trends for a diverse range of thiol nucleophile addition reactions at two separate sites on Aurora-A, and we also highlight limitations when using thiol nucleophiles that contain basic functional groups. We show that chemical modification of cysteine residues is possible not only on a flexible surface-exposed loop...

Selective functionalization of carbon nanotubes

Strano, Michael S.; Usrey, Monica; Barone, Paul; Dyke, Christopher A.; Tour, James M.; Kittrell, Carter W.; Hauge, Robert H.; Smalley, Richard E.
Fonte: Universidade Rice Publicador: Universidade Rice
ENG
Relevância na Pesquisa
46.26%
The present invention is directed toward methods of selectively functionalizing carbon nanotubes of a specific type or range of types, based on their electronic properties, using diazonium chemistry. The present invention is also directed toward methods of separating carbon nanotubes into populations of specific types or range(s) of types via selective functionalization and electrophoresis, and also to the novel compositions generated by such separations.

Methods for selective functionalization and separation of carbon nanotubes

Strano, Michael S.; Usrey, Monica; Barone, Paul; Dyke, Christopher A.; Tour, James M.; Kittrell, Carter W.; Hauge, Robert H.; Smalley, Richard E.; Marek, Irene Morin
Fonte: Universidade Rice Publicador: Universidade Rice
ENG
Relevância na Pesquisa
46.26%
The present invention is directed toward methods of selectively functionalizing carbon nanotubes of a specific type or range of types, based on their electronic properties, using diazonium chemistry. The present invention is also directed toward methods of separating carbon nanotubes into populations of specific types or range(s) of types via selective functionalization and electrophoresis, and also to the novel compositions generated by such separations.

Nanopatterning and functionalization of phospholipid-based Langmuir-Blodgett and Langmuir-Schaefer films

Tang, Nathalie Y.-W.
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
EN
Relevância na Pesquisa
36.15%
Durant les dernières décennies, la technique Langmuir-Blodgett (LB) s’est beaucoup développée dans l’approche « bottom-up » pour la création de couches ultra minces nanostructurées. Des patrons constitués de stries parallèles d’environ 100 à 200 nm de largeur ont été générés avec la technique de déposition LB de monocouches mixtes de 1,2-dilauroyl-sn-glycéro-3-phosphatidylcholine (DLPC) et de 1,2-dipalmitoyl-sn-glycéro-3-phosphatidylcholine (DPPC) sur des substrats de silicium et de mica. Afin d’amplifier la fonctionnalité de ces patrons, la 1-palmitoyl-2-(16-(S-methyldithio)hexadécanoyl)-sn-glycéro-3-phosphatidylcholine (DSDPPC) et la 1-lauroyl-2-(12-(S-methyldithio)dodédecanoyl)-sn-glycéro-3-phosphatidylcholine (DSDLPC) ont été employées pour la préparation de monocouches chimiquement hétérogènes. Ces analogues de phospholipide possèdent un groupement fonctionnel méthyldisulfide qui est attaché à la fin de l’une des chaînes alkyles. Une étude exhaustive sur la structure de la phase des monocouches Langmuir, Langmuir-Schaefer (LS) et LB de la DSDPPC et de la DSDLPC et leurs différents mélanges avec la DPPC ou la DLPC est présentée dans cette thèse. Tout d’abord, un contrôle limité de la périodicité et de la taille des motifs des stries parallèles de DPPC/DLPC a été obtenu en variant la composition lipidique...

Preferential functionalization on zigzag graphene nanoribbons: First-principles calculations

Lee, Hoonkyung
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 15/08/2010
Relevância na Pesquisa
36.49%
We investigate the functionalization of functional groups to graphene nanoribbons with zigzag and armchair edges using first principles calculations. We find that the formation energy for the configuration of the functional groups functionalized to the zigzag edge is ~0.2 eV per functional group lower than that to the armchair edge. The formation energy difference arises from a structural deformation on the armchair edge by the functionalization whereas there is no structural deformation on the zigzag edge. Selective functionalization on the zigzag edge takes place at a condition of the temperature and the pressure of ~25 oC and 10-5 atm. Our findings show that the selective functionalization can offer the opportunity for an approach to the separation of zigzag graphene nanoribbons with their solubility change.

Selective Functionalization of Halogens on Zigzag Graphene Nanoribbons: A Route to the Separation of Zigzag Graphene Nanoribbons

Lee, Hoonkyung; Cohen, Marvin L.; Louie, Steven G.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 15/08/2010
Relevância na Pesquisa
36.13%
Using the ab initio pseudopotential density functional method, we investigate the functionalization of halogen molecules into graphene-based nanostructures with zigzag and armchair edges. We find that halogen molecules adsorb through chemisorption on the zigzag edge carbon atoms with a binding energy of ~1-5 eV and their adsorption on a perfect zigzag edge is preferred, in sharp contrast to physisorption on the armchair edge and elsewhere where they adsorb with a binding energy of ~0.07 eV. We suggest that our findings would be utilized for an approach to the separation of zigzag graphene nanoribbons with regular edges with the change of the solubility of the functionalized nanoribbons.; Comment: 15 pages, 4 figures

Selective metal deposition at graphene line defects by atomic layer deposition

Kim, Kwanpyo; Lee, Han-Bo-Ram; Johnson, Richard W.; Tanskanen, Jukka T.; Liu, Nan; Kim, Myung-Gil; Pang, Changhyun; Ahn, Chiyui; Bent, Stacey F.; Bao, Zhenan
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 20/10/2014
Relevância na Pesquisa
36.11%
One-dimensional defects in graphene have strong influence on its physical properties, such as electrical charge transport and mechanical strength. With enhanced chemical reactivity, such defects may also allow us to selectively functionalize the material and systematically tune the properties of graphene. Here we demonstrate the selective deposition of metal at chemical vapour deposited graphene's line defects, notably grain boundaries, by atomic layer deposition. Atomic layer deposition allows us to deposit Pt predominantly on graphene's grain boundaries, folds, and cracks due to the enhanced chemical reactivity of these line defects, which is directly confirmed by transmission electron microscopy imaging. The selective functionalization of graphene defect sites, together with the nanowire morphology of deposited Pt, yields a superior platform for sensing applications. Using Pt-graphene hybrid structures, we demonstrate high-performance hydrogen gas sensors at room temperatures and show its advantages over other evaporative Pt deposition methods, in which Pt decorates graphene surface non-selectively.; Comment: 27 pages, 6 main figures

Biomimetic mineralization: encapsulation in calcium carbonate shells

Oliveira, Susana Costa de
Fonte: Universidade Nova de Lisboa Publicador: Universidade Nova de Lisboa
Tipo: Dissertação de Mestrado
Publicado em /09/2015 ENG
Relevância na Pesquisa
46.26%
Calcium carbonate biomineralization is a self-assembly process that has been studied to be applied in the biomedical field to encapsulate biomolecules. Advantages of engineering mineral capsules include improved drug loading efficiencies and protection against external environment. However, common production methods result in heterogeneous capsules and subject biomolecules to heat and vibration which cause irreversible damage. To overcome these issues, a microfluidic device was designed, manufactured and tested in terms of selectivity for water and oil to produce a W/O/W emulsion. During the development of this work there was one critical challenge: the selective functionalization in closed microfluidic channels. Wet chemical oxidation of PDMS with 1M NaOH, confirmed by FTIR, followed by adsorption of polyelectrolytes - PDADMAC/PSS - confirmed by UV-Vis and AFM results, render the surface of PDMS hydrophilic. UV-Vis spectroscopy also confirmed that this modification did not affect PDMS optical properties, making possible to monitor fluids and droplets. More important, with this approach PDMS remains hydrophilic over time. However, due to equipment constrains selectivity in microchannels was not achieved. Therefore, emulsion studies took place with conventional methods. Several systems were tried...